Start at the back, what does your fuel pump produce in litres per minute ? This is normally the first link in the chain when more fuel is required, not always but in general.
After market fuel pumps generally require direct battery voltage to get the benefits from them. This is because lots of manufacturers install a low level regulator which limits voltage to 9v and the after market pumps like a Walbro need 12v to operate properly.
Then there's a fuel pressure regulator, stock items don't like the newly acquired pressure and can become unstable.
Injectors, sizing & pressure. I have unfortunately lost the link I had for working out your requirements, I'm sure I even put it on here some time back, I'll have a look and see if I can find it. [I'll have a look when time permits]
Control, as Matt has suggested, a stand alone is without doubt a superb item but you can successfully get the control you need from a patch in item such as a MAP2 ECU,[a newer item may be available by now] these allow full fuel control and timing adjustment and the removal of the stock MAF.
You will need to put the car on a rolling road whatever you add but you can do a lot of the basic mapping from a laptop to get you up and running.
I'm sure there's stuff I've missed, my reply is rather brief as my time is short today.